Borers are used for finishing holes already formed in parts and generally comprise an elongate body having a cutting blade or insert housed in a groove in the end of the body. The other end of the body may be tapered to engage a machine tool spindle.
The cutting blade or insert may be held in the groove by means of a clamping plate of the type described in U.S. Pat. No. Re. 34,054, or may be held in position by means of clamping screws, the heads of which clamp the insert against the borer body as the screw is tightened, as is shown in EP 0650 792-A. This document discloses a reamer in which the screw head has a front surface that is convex and engages in a longitudinally extending concave groove in the surface of the insert. Such a locking system locates and holds the insert against transverse movement but does not locate and hold the insert longitudinally. The insert is typically located by abutment of one end face against a stop pin in the groove.